1. Technical Field
The present invention relates to a micro electro mechanical systems (MEMS) device.
2. Description of the Related Art
A micro electro mechanical systems (MEMS) is a technology of manufacturing a micro mechanical structure such as a very large scale integrated circuit, a sensor, an actuator, or the like, by processing silicon, crystal, glass, or the like. MEMS devices have precision of a micrometer ( 1/1,000,000 meter) or less and may be structurally mass-produced as a micro product at a low cost by applying a semiconductor micro process technology of repeating processes such as a deposition process, an etching process, and the like.
Among the MEMS devices, a sensor has been used in various applications, for example, a military application such as an artificial satellite, a missile, an unmanned aircraft, or the like, a vehicle application such as an air bag, electronic stability control (ESC), a black box for a vehicle, or the like, a hand shaking prevention application of a camcorder, a motion sensing application of a mobile phone or a game machine, a navigation application, or the like.
The sensor generally adopts a configuration in which a mass body is adhered to an elastic substrate such as a membrane, or the like, in order to measure acceleration, angular velocity, force, or the like. Through the configuration, the sensor may calculate the acceleration by measuring inertial force applied to the mass body, calculate the angular velocity by measuring Coriolis force applied to the mass body, and calculate the force by measuring external force directly applied to the mass body.
In detail, a scheme of measuring the acceleration and the angular velocity using the sensor is as follows. First, the acceleration may be calculated by Newton's law of motion “F=ma”, where “F” represents inertial force applied to the mass body, “m” represents a mass of the mass body, and “a” is acceleration to be measured. Among others, the acceleration a may be obtained by sensing the inertial force F applied to the mass body and dividing the sensed inertial force F by the mass m of the mass body that is a predetermined value. Further, the angular velocity may be obtained by Coriolis force “F=2mΩ×v”, where “F” represents the Coriolis force applied to the mass body, “m” represents the mass of the mass body, “Ω” represents the angular velocity to be measured, and “v” represents the motion velocity of the mass body. Among others, since the motion velocity V of the mass body and the mass m of the mass body are values known in advance, the angular velocity Ω may be obtained by detecting the Coriolis force (F) applied to the mass body.
Meanwhile, the sensor according to the prior art includes beams extended in an X axis direction and a Y axis direction in order to drive the mass body or sense displacement of the mass body, as disclosed in the following Prior Art Document (Patent Document). However, in the sensor according to the prior art, as the displacement of the mass body increases, tension acting on the beam rapidly increases. When the tension of the beam increases as described above, rigidity of the beam also increases, such that driving displacement or sensing displacement of the mass body is limited. In addition, when the rigidity of the beam increases, a resonance frequency is changed, such that noise increases.